I added 15 images to a field and copied the result below from the database. Looks like the images and searchStr values are in a different order than as loaded. Not sure if this has anything to do with your issue, just an observation.
[
{"name":"files\/img001_y4ypdem3.jpg","usrName":"img001.jpg","size":39888,"type":"image\/jpeg","thumbnail":"files\/thimg001_9x5jgbem.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2496,"searchStr":"img001.jpg,!img002.jpg,!img004.jpg,!img003.jpg,!img007.jpg,!img006.jpg,!img005.jpg,!img014.jpg,!img008.jpg,!img009.jpg,!img011.jpg,!img015.jpg,!img012.jpg,!img010.jpg,!img013.jpg,!:sStrEnd"},
{"name":"files\/img002_03gl72i8.jpg","usrName":"img002.jpg","size":40662,"type":"image\/jpeg","thumbnail":"files\/thimg002_robxxgwt.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2534},
{"name":"files\/img004_xmrlprac.jpg","usrName":"img004.jpg","size":30455,"type":"image\/jpeg","thumbnail":"files\/thimg004_f92fo3dq.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2206},
{"name":"files\/img003_i899y5zz.jpg","usrName":"img003.jpg","size":38848,"type":"image\/jpeg","thumbnail":"files\/thimg003_awsdacol.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2369},
{"name":"files\/img007_k5qapy7n.jpg","usrName":"img007.jpg","size":33131,"type":"image\/jpeg","thumbnail":"files\/thimg007_z0zusonu.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2106},
{"name":"files\/img006_k37h8o98.jpg","usrName":"img006.jpg","size":31306,"type":"image\/jpeg","thumbnail":"files\/thimg006_18076ax5.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2443},
{"name":"files\/img005_kpwu77es.jpg","usrName":"img005.jpg","size":44263,"type":"image\/jpeg","thumbnail":"files\/thimg005_m690xm9i.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2807},
{"name":"files\/img014_eelbmf52.jpg","usrName":"img014.jpg","size":37109,"type":"image\/jpeg","thumbnail":"files\/thimg014_ipfp8vsc.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2008},
{"name":"files\/img008_jkhjwul8.jpg","usrName":"img008.jpg","size":43178,"type":"image\/jpeg","thumbnail":"files\/thimg008_6hlydhqq.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2678},
{"name":"files\/img009_5k2hd2kh.jpg","usrName":"img009.jpg","size":35825,"type":"image\/jpeg","thumbnail":"files\/thimg009_6qhubkg9.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2136},
{"name":"files\/img011_tvvj6f1h.jpg","usrName":"img011.jpg","size":73191,"type":"image\/jpeg","thumbnail":"files\/thimg011_dtgy2u5o.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2378},
{"name":"files\/img015_ygssuda6.jpg","usrName":"img015.jpg","size":66873,"type":"image\/jpeg","thumbnail":"files\/thimg015_0jwsotpy.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":3307},
{"name":"files\/img012_wrw4b2rn.jpg","usrName":"img012.jpg","size":82916,"type":"image\/jpeg","thumbnail":"files\/thimg012_9o8t482x.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2593},
{"name":"files\/img010_2gxi353u.jpg","usrName":"img010.jpg","size":78021,"type":"image\/jpeg","thumbnail":"files\/thimg010_c66z5vlx.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":2794},
{"name":"files\/img013_awaei61t.jpg","usrName":"img013.jpg","size":37418,"type":"image\/jpeg","thumbnail":"files\/thimg013_8shd8hs5.jpg","thumbnail_type":"image\/jpeg","thumbnail_size":1842}]